Stable Crack Extension Rates in Ductile Materials: Characterization by a Local Stress-Intensity Factor

A theory is presented for the steady-state propagation of a Mode III crack in a ductile material. The inelastic deformation of the matrix material and the cracking mechanism are both described by real-time rate constitutive laws. The theory leads to realistic nonsingular stresses and relates the crack-tip velocity v to the apparent stress-intensity factor KA that characterizes the remote loading. It is shown that the crack-tip behavior is characterized by a local stress-intensity factor K and that the inelastic deformation is described by a plastic stress-intensity factor KP such that K = KA + KP. These stress-intensity factors are all well defined even though the stress is nonsingular.